The invention relates to a projection exposure device, in particular for microlithography, to produce an image of an object positioned in an object plane in an image plane with a radiation source emitting projection radiation, with illumination optics positioned in the ray path between the radiation source and the object plane and projection optics positioned in the ray path between the object plane and the image plane.
Where three dimensional structures are to be projected, for example in the case of transmitting three dimensional structures from a recticle onto a wafer in connection with micro-lithography, it has been shown that it is a matter not only of homogeneous as possible illumination of the object plane but also of well-defined distribution of the illumination angle in the object plane, i.e. the angles under which the projection radiation strikes the object plane. The illumination angle distribution to be set depends on how the structures are positioned on the recticle and what extension they have perpendicular to the object plane. For different recticle-structures therefore different illumination angle distributions to be preset for optimum projection can result.
With projection exposure devices known in the market illumination intensity is measured by a photosensor, which for example picks up the reflection of an optical component of the projection exposure device.
It is not possible to measure an illumination angle distribution with such a photosensor.
The present invention relates to further developments of a projection exposure device of the type described at the beginning so that the illumination angle distribution can be calculated and brought near to the desired distribution.
Accordingly, the present invention provides a projection exposure device in which:
a) a detection device is provided which measures the illumination angle distribution of the projection radiation in a field plane;
b) the detection device communicates via at least one control device with at least one manipulator to move at least one optical component within the ray path of the projection radiation; and
c) at least one of the optical components is designed and arranged in the ray path of the projection radiation in such a way that the illumination angle distribution changes as a result of its controlled movement.
In this case for example projection light optical wavelengths, UV projection light or even EUV projection radiation, for example radiation with a wavelength of 13 nm, can be used as projection radiation.
An actual state of the illumination angle distribution is measured with the detection device. Measurement of the illumination angle distribution at the same time enables a further series of information which is of interest to the projection to be evaluated. For example it allows in a simple way the telecentre square distribution to be calculated in the measured field plane. In addition with the measured illumination angle distribution the distribution of the numerical aperture of the illumination light as well as the illumination intensity distribution is known via the measured field plane.
The field plane, the illumination angle distribution of which is measured, can in this case be the object plane itself or a plane conjugated to this.
With the aid of the control device and at least one allocated manipulator it is possible via movement of at least one optical component to adapt the measured illumination angle distribution to a standard value. In this case one manipulator or several manipulators can be provided for a component. With the aid of such adaption it is possible for example depending on the structure to be projected to obtain optimum illumination of the object.
The detection device can have: an aperture, which can be positioned in a field plane, a position resolving sensor to record the radiation passing through the aperture and a drive mechanism to move the aperture together with the sensor in the field plane. With this relatively simple configuration, precise measurement of the illumination angle distribution in the field plane is possible. The diameter of the aperture in this case determines the position resolution in the field plane. The detection device is moved over the total field plane to be measured by means of the drive mechanism. With such a detection device the illumination intensity distribution in the field plane can also be measured.
The position resolving sensor can be a CCD-array. A CCD-array is light-sensitive and has a high position resolution. With the aid of known coatings the sensitivity of the CCD-array can be extended as far as the illumination wavelength range of the UV wavelengths interesting for micro-lithography. If only a minimum position resolution is required for the position resolving sensor, this can also be designed for example as a simple quadrant detector.
At least one optical deflection element can be positioned in the ray path between the aperture and the position resolving sensor. This reduces the overall depth of the detection device in the direction of the optical axis. Precisely in the case of projection exposure devices, with high structural integration, the space in which the detection device can be placed is very restricted.
At least one filter can be positioned in the ray path between the aperture and the position resolving sensor. The filter can include a spectral filter, so that for example only the interesting illumination wavelength is allowed through. An example of such a filter is a notch filter. Other wavelengths, which could interfere with the measurement under certain circumstances, are suppressed.
Alternatively or in addition, the filter can have a grey filter or a reflection filter to attenuate a greater wavelength range in a neutral way.
At least one lens can be positioned in the ray path between the aperture and the position resolving sensor. Such a lens can for example increase the resolution of the detection device.
An optical component acting in conjunction with the manipulator can be a filter. With a filter it is possible to achieve specific range-wise attenuation of the projection light bundle. The filter can be designed as an absorption or reflection filter. Instead of a filter with a moveable filter component, in the case of which when the moveable filter component is moved the transmission in the filter plane is altered, an exchange holder can be provided for a number of replaceable filters.
The filter can be placed in the vicinity of a field plane of the projection optics. If the filter is placed in or near a field plane in practice it only influences the illumination intensity distribution in the object plane, not however the illumination angle distribution there.
Alternatively the filter can be positioned in the vicinity of a pupil plane of the projection optics. Such a filter positioned in or near a pupil plane of the projection optics influences the illumination intensity in this plane and as a result serves to determine the illumination angle distribution in the object plane, while the illumination intensity distribution in the object plane is not influenced or hardly influenced at all. Accordingly the illumination angle distribution is changed by displacing the filter or the moveable filter component with the aid of the manipulator.
At least one Z-manipulator can be provided for an optical component of the projection optics as manipulator. The Z-direction in this case is the direction in which the optical axis of the projection optics runs. Also it is possible to change the illumination angle distribution by means of the Z-manipulation of optical components.
Such an optical component can be a lens. With the aid of a Z-manipulatable lens, apart from the illumination angle distribution, in addition an image error of the projection exposure device can be corrected.
Another kind of Z-manipulated optical component can be an axicon. With the aid of an axicon a controlled changeable rotation-symmetrical illumination angle distribution can be set in a simple way.
A manipulatable optical component can be a device to adjust the radiation source. With the aid of the adjustment device, for example the divergence of the projection radiation bundle radiated from the radiation source can be adjusted. This is an additional influence parameter for the illumination angle distribution.
The manipulator can have a piezo element. With piezo elements reproducible and precise displacement can be achieved. If several piezo elements are used to manipulate an optical component, apart from the Z-position the inclination of the optical component can be set against the optical axis.
Apart from the aforementioned manipulatable optical components, others are again conceivable to influence the illumination angle distribution. Examples of these are camera wedges which can be displaced against each other, tiltable or Z-manipulatable plan-parallel optical plates, aperture shutters with changeable opening or, in the case of catadioptric projection objectives, active mirrors.